./guide
fold.pro

Last modification date:

Thu Jun 2 23:56:08 2005

fold

procedure fold[, sig][, ref], [ftol=double]

Average two parts of in-band frequency switching (signal and reference phases, with the cal-switching phases already calibrated). Typically this happens after getfs. The two data containers are assumed to be in 0 and 1. It does not matter which data container containers which part since their relative distance in frequency is used to determine how one is shifted to align with the other. The result is always placed in data container 0.

The "ref" data container is shifted to align in sky frequency with the "sig" data container using dcshift and the two data containers are averaged - weighting each by the inverse of square of their system temperatures. The system temperature in the result is the weighted average of the two system temperatures.

Uses

dcfold data_free set_data_container

Version

$Id: fold.pro,v 1.6 2005/05/09 21:04:45 bgarwood Exp $

Parameters
sig in, optional integer (def. 0)	The index of the data container to use as the signal part in the average. The result will contain a copy of this data container's header information except for tsys as described above. The data at sig is overwritten by the result if sig is 0 (the default)
ref in, optional integer (def. 1)	The index of the data container to use as the reference part in the average. This data is shifted using dcshift to align with "sig" before averaging. The data in ref are never altered by this procedure.

Keywords

ftol in, optional double (def. 0.005)

The fractional channel shift tolerance. If the fractional part of the channel shift necessary to align the two parts is less than this value, no fractional shift as described in the documentation for dcshift will be done. It might be useful to turn off the fractional shift because it can cause aliases and ringing in the case of very strong lines or other sharp features. If ftol > 0.5 no fractional shifts will be done.